Device and method for determining the end pattern of filament wound pressure vessels



3,005,256 ERN 3 Sheets-Sheet 1 INVENTOR.

A T TOR NE E. YOUNG R/CHA D E. You/ve- OF FILAMENT WOUND PRESSUREVESSELS Ef J.

Oct. 24, 1961 DEvIcE AND METHOD FOR DETERMINING THE END PATT Filed Nov.26, 1957 n 2 H 2 ll| 8 II n! .n 4! 2w 2 l M N? I H 5 L He A H I M B 2 4H 2 H 4 nunwll ll "I 2 I I 3 l 9 8 2 n 2 4 I II W I 3 I m 2 2 2 Oct. 24,1961 R. E. YOUNG 3,005,256

DEVICE AND METHOD FOR DETERMINING THE END PATTERN OF FILAMENT WOUNDPRESSURE VESSELS Filed Nov. 26, 1957 3 Sheets-Sheet 2 INVENTOR. AQ/CHA DE. You/va- ATTORNEY Oct. 24, 1961 R. E. YOUNG 3,005,256

DEVICE AND METHOD FOR DETERMINING THE END PATTERN OF FILAMENT WOUNDPRESSURE VESSELS Filed Nov. 26, 1957 3 Sheets-Sheet 3 17 /9 l 2e 9 .6 M

' mm nu u n n 5311 1| 1| i f 2o ll INVENTOR. 2 lQ/CHA/QD E. YOUNG ATTOR/VE Y,

United States Patent 3,005,256 DEVICE AND METHOD FOR DETERMINING THE ENDPATTERN OF FILAMENT WOUND PRES- SURE VESSELS Richard E. Young, RockyHill, N.J., assignor, by mesne assignments, to Hercules Powder Company,Wilmington, Del., a corporation of Delaware Filed Nov. 26, 1957, Ser.No. 699,078 14 Claims. (Cl. 29407) This invention relates to method andapparatus for determining the end pattern of filament wound pressurevessels.

In the forming of pressure vessels by the winding of helical patterns offilaments, maximum structural performance can only be achieved when thetension load in each filament is constant for every location in thestructure. To achieve this, it becomes apparent that as the spacing ofthe filament windings in the end formation of the vessel diminishes, theradius of curvature of the filament must increase. To fit thisrelationship, the end shape of the element must be approximatelyeliptical, with its maximum radius of curvature at the winding terminalzone adjacent the pole.

To generate a complete end shape, particularly where it is integral witha helically wound cylinder, by employing the returned ends of thehelixesinvolved in the wind ing of the cylinder, presents considerableof a problem. This problem is, however, overcome by the method andapparatus of the invention. Briefly stated, the method of the inventioninvolves the simulation of the end pattern for the desired structure byemploying a frame simulating a cylindrical body of a vessel with an endfitting suitably mounted in predetermined position as part of that frameand the development of a netting structure by applying windings over theframe and about the end fitting. The netting must be laced on by handunder such tension as readily becomes apparent to the user of thedevice.

When the netting structure is completed, the support for the end fittingis removed and the netting structure is a method for predetermining thecontour of an ovaloid end for pressure vessels.

Another object is to provide a method for predetermining such contourfor any set of design conditions.

Another object is to provide for the contouring of ovaloid ends forvessels made of helical filament windings.

Still another object is to provide a method for predetermining the shapeof such end to provide constant fibre stress in such windings.

Still another object is to provide a method for determining an endpattern of filament wound pressure vessels which may be varied as tosize.

A further object is to provide apparatus for predetermining the desiredend pattern for a filament wound pressure vessel.

Another object is to provide such apparatus which is simple to employand fool-proof in its representation.

Further and more detailed objects will in part be obvious and in part bepointed out as the description of the invention taken in conjunctionwith the accompanying drawing proceeds.

In that drawing:

FIG. 1 is a front elevation of the apparatus of the invention assembledin upright position ready for use.

FIG. 2 is an elevation of apparatus in reversed position with partsthereof removed.

FIG. 3 is a top plan view of the device as shown in FIG. 2.

FIG. 4 is an elevation of the closing plate supporting stem assembly perse.

FIG. 5 is an exploded view of the receiving ring, base ring and closingplate in their relative positions.

loaded from within by the inflating of an air-tight membrane andadjustment of the tension on the netting to bring the surface contour tothe precise shape required for constantfiber stress and maximumstructural efficiency. Important in this is the adjusting of thestructure until the radial section of the curved surface generated has aterminal slope whichbrings it tangent to the simulated cylindrical body.I

i Not only does this method enable the end formation to be determinedfor uniform resistance to internal pressure, but is. also serves forexamination of the effect of external forces. This is achieved byapplying a force to the end fitting which is in proper proportion to theinflation pressure. This will show the effect of theforce on the surfaceprofile slopejand profile adjustment can be made if needed by adjustingthe netting tension.

When the proper end contour has been attained, shadowgraphs of it may beformed on a fiat surface and by rotating thedevice the diflerentprofiles projected may be averaged out graphically to give the propermean curvature. e e

Once the desired profile is determined, it may be adjusted to size bythe use of some means, such as a pantograph, and may becorrected forsuch things as wall fittings and-thickness to be used. A mandrel for usein forming thevessel by helical windings, as taught in my applicationSerialNo. 374,600, filed August 17, 1953 for Filament Wound HollowElements and Methods for Making Same (now US. Patent No. 2,843,153,issued July 15, 1958),.is made up with ends contoured in accordance withthe end pattern determined.

It is, accordingly, an object of the invention to provide FIG. 6 is aview similar to FIG. 1 but showing the apparatus with the nettingstructure in place and with the inflatable member in inflated conditiontherewithin.

FIG. 7 is a fragmentary vertical section of the rings with the filamentslaced therein taken on line 4-4- of FIG. 6 and looking in the directionof the arrows.

FIG. 8 is a bottom plan View of the apparatus as viewed from beneath inFIGS. 1 and 6; and

FIGS. 9 and 10 are representative shadowgraphs illustrating the mannerin which simulated end contours are taken off for use in the forming ofmandrels.

The apparatus of the invention and for carrying out the method thereofhas a fixed base ring 1 which is supported by a plurality of identicallegs 2, here shown as three in number. These legs are double ended inthe sense that they are attached to the ring 1, at the position 3,extend down to return bent portions 4 and then extend upwardly to theirends 5. These ends are well above the base ring 1 and the adjustablereceiving ring 6, for reasons that will appear hereinafter.

The adjustable receiving ring 6 of the same diameter as-the base ring 1and axially aligned therewith is mounted above the base ring 1, asviewed in FIG. 1, for axial adjustment with respect thereto. Thatadjustment is effected by pairs of screws 7 and 8 seated in the basering 1 and positioned in pairs in spaced positions around the base ring.Three pairs of these screws, as seen in FIG. 5, are adequate. The screw7 of each pair serves to pull the ring 6 down with respect to the ring1, whereas the screw 8 serves to force it upward. Screw 7 is seated downinto the ring 1 from its upper surface, having its head engaged againsta shoulder. That head is formed to receive an Allen wrench, and liesabove the bottom surface of the base ring 1. An opening in the ringcommunicates with the head.

The base ring 1 is formed with a central opening therethrough, as shownat 9 in FIGS. 5 and 8. That opening is normally closed by means of theend plate 10 suitably secured concentrically to the undersurface of thebase ring 1 by a plurality of screws 11, here shown as three in number.In the initial stage of use of the apparatus for carrying out the methodof the invention, as shown in FIG. 1, the plate serves as a support 'fora center stem 12. That stem, positioned axially of the device, issecured to the plate where it passes through the center thereof, asindicated by the nuts 13 and 13a, thus the stem 12 cannot move up ordown with respect to the plate '10 from its set position. At its upperend the stem 12 carries suitable means for positioning an end fitting atthe preselected height with respect to the receiving ring 6. Theprovision here shown for mounting an end fitting is a mounting plate .14locked in axial position on the stem 12 by means such as nuts 15 and 16.Adjustment of the height of the plate 14 is, of course, provided for bymovement of the nuts .15 and 16 and additionally by movement of the nut.13 and its counterpart 13a on the inner side of the plate 10, ifmovement is desired there.

The height of the polar fitting 1.7, within reasonable limits, is easilydeterminable after the device has been tried a few times. Fundamentally,the positioning of it should be such that when a netting pattern ofthreads is laid across the upper surface 18 of the base of the fittingtangent to its neck 19 under generally uniform tension, those threadswill become tangent to the cylinder of the slots in the ring 6 at thebase of those slots. When such netting is suitably convexly outwardlycurved by the inflation of an internal membrane, minor variations in theinflated contour can be elfected by the adjustment of the ring '6 withrespect to the ring 1.

Coming now to the application of threads to form the netting structure,it will be seen that both the base ring 1 and the receiving ring 6 areprovided With *a plurality of grooves extending parallel to the .axis ofthe rings. Furthermore, the grooves 20 of the ring '1 and those 21 ofthe ring 6 are in alignment. The depth and direction of extension ofthese grooves are best shown in the cross sectional view of FIG. 3.Coming back to FIG. 1, it will be seen that the threads 22 are lacedover the surface 13 of the fitting 17, extend down through the slots 21,through the slots 20 mated therewith and across beneath the ring 1 for asuitable number of slots until, when brought back upwardly again, theywill again lie tangent to the outer surf-ace of the neck 19 as theyagain pass over the end fitting 18. Actually, the forming of the nettingstructure can commence at the bottom by anchoring the beginning of thethread to one of the legs 2 and proceeding from there.

Though only a few of the threads are shown in FIGS. 1 and 2, for thepurposes of illustration, it is to be understood that threads will bedrawn up through all of the slots 20 and 21 so as to form a completepattern, as seen in FIG 6, except that, until an inflatable member isemployed within the netting, the threads will not be expanded outwardlyto the curved formation .shown in FIG. 6.

Once all of the threads have been applied to the device in its FIG. 1condition in order to form the complete netting, the next step is toturn the device upside down removing the plate 10 taking with it thestem 12 which has supported the fitting '17 in its upright position.Then the device will appear as seen in FIGS. 2 and 3. The fitting 17,being carried by the netting, will remain in place so long as the deviceis left in this upside down position. The next step then is to load thethreads of the netting structure to bring the surface contour to theprecise shape required for constant fiber stress and maximum structuralefliciency.

This is done by the insertion of a suitable inflatable member downthrough the opening 9 in the ring 1 and through the correspondingopening 25 in the ring 6. This member, which may merely be a balloon 26of suflicient strength for the job, is seated within the basket formedby the netting of the threads 22. The stem 12 having been removed fromthe plate 10 by the removal of the nut 13, the neck 26a of the balloonis passed through the opening 27 formerly occupied by that stem. Thenthe plate 19 is reapplied to the undersurface of the base plate 1, theballoon is suitably pumped up to load the netting structure and bringthe surface contour of the netting and balloon to the precise shaperequired for constant fiber stress and maximum structural eificiency.This will obviously take place in the natural contouring of the nettingas the balloon or other inflatable member is inflated.

The term closing end position or position of the closing end as usedherein and in the claims with reference to the end pattern means theposition onthe axis of the end pattern where the pattern 'or anyextension thereof intersects the axis.

If after the inflation of the balloon it appears the contouring of thenetting is not such as to produce the desired ideal condition, thecontour can be adjusted to a small degree, and normally to a suflicientdegree, by adjusting the position of the ring .6 with respect to thering 1 through the action of the appropriate ones of the screws 7 and 8.This idea-l condition is 0116111 which the profile of the nettingformation will be tangent to the cylinder generated by the bottoms ofthe grooves in the ring '6 at the upper face of that ring.

Obviously the balloon when inflated will hold up the end fitting 17 and,further than this, the mounting of the end fitting may be employed toexamine the efiect of external forces on the end formation as simulatedby the netting structure. This is achieved by applying force to the endfitting proportioned to the inflation pressure in the same relation thatthe anticipated force would be expected to bear to the resistance todistortion provided by the end formation of the eventual vessel.

Once the curvature of the simulated end formed out of the inflatednetting pattern 22 is determined, shadowgraphs thereof can be taken atdifferent positions, as indicated at 28 in FIG. 9 and 29 in FIG. 10. Asmany of these .can be taken as desired and they can be superposed andaveraged out to give an average curvature. That average curvature canthen be employed for the forming of the ends of a suitable mandrel foruse in the winding of the vessel in question.

Though a single device of somewhat limited adjustability maybe employedfor carrying out of the method of the invention, it 'is to. beunderstood that mandrels for use in the fabrication of vessels ofdifferent sizes with different sized ends can be readily constructed bytracing the average curve determined from the .use of the device asdescribed by means of a pantograph and thus enlarging or reducing thesize of the end as desired. Then, again, the device permits a reasonablerange of positioning as regards the end fitting due to the adjustabilityof the positioning of that fitting on the stem 12 and the adjustabilityof the position of the stem 12 with respect to the plate 10.

Though in the foregoing a particular embodiment of apparatus has beenshown for exemplifying the apparatus aspect of the invention and forcarrying out the method thereof, it .isof course to be understood thatthis showing is merely for illustrative purposes and that other forms ofapparatus may be devised without departing from the spirit and scope ofthe invention from either an apparatus or method standpoint. Also,though .the detailing of the method as such has not, in the foregoingbeen par ticularly sparated from the description of the device and theuse thereof, it is believed that the steps involved in the performanceof the method have been sufficiently brought out that it would be mererepetition to relate them per se.

Having described my invention, what I claim as new and desire to secureby Letters Patent is: V

1. The method of determining end patterns of filament wound pressurevessels having a central axis which comprises, establishing the circleof maximum circumference of the end pattern in a plane with said axispassing through the center of said circle and at right angles to saidplane, establishing a position on said axis in spaced relation withrespect to said plane, which position is approximately the positionofthe closing end of said end pattern on said axis; establishing arelatively smaller circle than said circle of maximum circumferencehaving its center at about said approximate closing end position andlying in a plane perpendicular to said axis, passing thread between saidcircle of maximum circumference and said relatively smaller circle toform a net-work of thread therebetween, and expanding with uniformpressure said net-work outwardly from the inner side thereof to form anend curvature wherein all the threads are in uniform tension.

2. The method as in claim 1 wherein the thread is passed undersubstantially uniform tension between said circle of maximumcircumference and said relatively smaller circle to form a net-work ofthreads therebetween.

3. The method as in claim 1 wherein said thread is substantiallycontinuous.

4. The method as in claim 1 wherein the step of expanding with uniformpressure said net-work outwardly from the inner side thereof is effectedby inflating a balloon interiorly of said net-work.

5. The method as in claim 1 wherein the relatively smaller circle issupported and the support is removed prior to expanding with uniformpressure the net-work outwardly.

6. The method of determining end patterns of filament wound pressurevessels having a central axis which comprises, establishing the circleof maximum circumference of the end pattern in a plane with said axispassing through the center of said circle and at right angles to saidplane, establishing a position on said axis in spaced relation withrespect to said plane, which position is approximately the position ofthe closing end of said end pattern on said axis, establishing arelatively smaller circle than said circle of maximum circumferencehaving its center at about said approximate closing end position andlying in a plane perpendicular to said axis, passing threads from saidcircle of maximum circumference to said relatively smaller circle andthence to other positions on said circle of maximum circumference toform a network of threads therebetween, securing said threads at saidcircle of maximum circumference, and expanding with uniform pressuresaid net-work outwardly from the inner side thereof to form an endcurvature wherein all the threads are in uniform tension.

7. The method of determining end patterns of filament wound pressurevessels having a central axis which comprises, establishing the circleof maximum circumference of the end pattern in a plane with said axispassing through the center of said circle and at right angles to saidplane, establishing a position on said axis in spaced relation withrespect to said plane, which position is approximately the position ofthe closing end of said end pattern on said axis, seating in uprightposition with respect to said plane a fitting having a cylindrical neckand a flanged base, said fitting being seated coaxially with saidcentral axis and having its flanged base substantially at saidapproximate closing end position, passing threads from positions on saidcircle across said flanged base tangent to said cylindrical neck to forma net-work of threads therebetween, securing said threads at saidcircle, removing the support for said fitting, and expanding withuniform pressure said net-work outwardly from the inner side thereof toform an end curvature wherein all the threads are in uniform tension.

8. The method of claim 7 wherein said threads are passed undersubstantially uniform tension from positions on said circle of maximumcircumference across said flanged base tangent to said cylindrical neckto form a net-work of threads therebetween.

9. The method as in claim 7 wherein said threads are passed frompositions on said circle of maximum circumference across said flangedbase tangent to said cylindrical neck and thence back to positions onsaid circle which are substantially diametrically opposite the startingpositions, respectively, to form a network of threads between saidfitting and said circle.

l0. The-method as in claim 9 wherein said threads are passed undersubstantially uniform tension from positions on said circle of maximumcircumference across said flanged base tangent to said cylindrical neckand thence back to positions on said circle which are substantiallydiametrically opposite the starting positions, respectively, to form anet-work of threads between said fitting and said circle.

11. The method of determining the end patterns of filament woundpressure vessels having a central axis, which comprises, establishingthe circle of maximum circumference of the end pattern in a plane withsaid axis passing through the center of said circle and at right anglesto said plane, establishing a position on said axis in spaced relationwith respect to said plane, which position is approximately the positionof the closing end of said end pattern on said axis, establishing arelatively smaller circle than said circle of maximum circumferencehaving its center at about said approximate closing end position andlying in a plane perpendicular to said axis, passing thread between saidcircle of maximum circumference and said relatively smaller circle toform a net-work of threads therebetween, expanding with uniform pressuresaid net-work outwardly from the inner side thereof to form an endcurvature wherein all of the threads are in uniform tension, projectinga shadow of said simulated end so formed onto a suitable receivingsurface and forming a mandrel with ends in accordance with said shadow.

12. The method as in claim 9 including, projecting a plurality of saidshadows from different radial positions of said end, averaging out thecurvatures of said shadows, and forming a mandrel from said averagedcurvature.

13. The method of determining end patterns of flla ment wound pressurevessels having a central axis which comprises, establishing the circleof maximum circumference of the end pattern in a plane with said axispassing through the center of said circle and at right angles to saidplane, establishing a position on said axis in spaced relation withrespect to said plane, which position is approximately the position ofthe closing end of said end pattern on said axis, establishing arelatively smaller circle than said circle of maximum circumferencehaving its center at about said approximate closing end position andlying in a plane perpendicular to said axis, passing thread undersubstantially uniform tension between said circle of maximumcircumference and said relatively smaller circle to form a net-work ofthreads therebetween, expanding with uniform pressure said networkoutwardly from the inner side thereof to form an end curvature whereinall the threads are in uniform tension, and adjusting the resultingstructure until the curves defined by axially sectioning the endcurvature so formed have terminal slopes which bring them tangent to asimulated cylinder formed by moving said circle of maximum circumferencealong said central axis.

14. The method of determining end patterns of filament wound pressurevessels having a central axis which comprises, establishing the circleof maximum circumference of the end pattern in a plane with said axispassing through the center of said circle and at right angles to saidplane, establishing a position on said axis in spaced relation withrespect to said plane, which position is approximately the position ofthe closing end of said end pattern on said axis, establishing arelatively smaller circle than said circle of maximum circumferencehaving its center at about said approximate closing end position andFlying in a plane perpendicular to .said axis,'passing thread betweensaid circle of maximum circumference and said relatively smaller circleto form a net-work :of thread' therebetween, expanding with uniformpressure said net-work outwardly from the inner side thereof to form anend curvature wherein all the threads are in uniform tension andadjusting the resulting structure to take into account the effectofexternal forces on the end curvature by applying force to the-endfitting appropriately proportioned to the (inflation pressure.

References Cited in the file of this ,patent 7 STATES PATENTS 7 RichardJuly 8, '192'4 Ferrand Oct. '29, 1929 Troiel Oct. 19, 1943 Alder'ferDec. 26, 1944 Seafle Jan. ,2, 1945 Lindsay Apr. 3, 1945 Duecy. May 1,1956 Tcorrected below.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nb, 005256I October 2 1961 Richard E, Young- It is hereby certified that errorappearsin fbhe above numbered patentre'quiring correction and that thesaid Letters Patent should read as Column 6 line 39 for the claimreference numeral ."9" read 11 Signed and sealed this 10th day of April1962.

(SEAL) Attest:

ERNEST W. SWIDER' DAVID L. LADD Attesting Officer Commissioner ofPatents

